1. Field of the Invention
This invention relates to a circuit arrangement for a stereo-hunting device in a stereo decoder in which not only a pilot tone, but also a sum signal and a difference signal of two reproduction signals are obtained from a received signal, and more particularly to such an arrangement in which, in a matrix operating with sum and difference formation, the sum and difference signals are converted to form the reproduction signals, and wherein only the sum signal is present in the case of a mono-received signal.
2. Description of the Prior Art
The usual frequency-modulated stereo-multiplex signal used for the transmission of two discrete information channels which, in stereo radio contain the information of two recording devices for left and right, and, accordingly, for two reproduction loud speakers for left and right, consist of three components. The first component is a sum signal (L+R) consisting of the left-hand information L and the right-hand information R in the frequency range from 30 Hz to 15 kHz. The second component is a difference signal (L-R) consisting of the left-hand information L and the right-hand information R, which is modulated onto a suppressed auxiliary carrier, for example 38 kHz. The frequency band for the difference signal (L-R) extends, with the lower and upper side band, from 23 kHz to 53 kHz. A third component serves to transmit a pilot tone of, for example, 19 kHz which permits the regeneration of the 38 kHz auxiliary carrier in the stereo decoder of the receiving device.
If only a mono-transmission takes place, then only the sum signal (L+R) exists. Normally, a signal is obtained from the pilot tone which permits an optimum display of the presence or the absence of a stereo transmission. When a user of a receiving device is searching for a stereo transmission, he must observe this optical display.